A validated population of male and female monkey breeders (M. nemestrina) contains 80 animals at high or at low risk for bad pregnancy outcomes. These outcomes include abortion, stillbirth, prematurity, low birth weight, and/or neonatal death. When subjected to stress during pregnancy conceptions from low risk breeders have a marked increase in abortions, while conceptions from high risk breeders are not further effected by the prenatal stressor. Low birth weight and/or premature offspring from these or similar breeders exhibit anomalies in growth, feeding behavior, diurnal cycles of activity and basic physiological functions, and aspects of learning and social behavior. We are using this population as an experimental model to (1) identify genetic, prenatal, perinatal, and postnatal factors which result in (2) offspring mortality, prematurity, and mental or social retardation or other disabilities, with the goal of (3) preventing bad pregnancy outcomes and their associated offspring abnormalities. To approach our overall goals we are conducting experiments having the following aims. (1) To identify factors causing abortions, prevent these abortions, and produce surviving offspring at high risk for developmental abnormalities. (2) To study the developmental effects of prematurity by delivering offspring from high and low risk parents at early gestational ages using C-section procedures. (3) To study the contribution of males to bad pregnancy outcomes and offspring abnormalities by breeding timed mated animals together who are of high and low risk. (4) To identify the interactive effects of parental risk, prenatal stress, perinatal condition of the newborn, and rearing under enriched vs. impoverished environmental conditions. (5) To assess the effects of newborn condition on maternal behavior and mother-infant transactions during the neonatal and early infancy periods. Our final aim (6) is to relate serological, infection, fertility, endocrine, and brain pathology findings to offspring abnormalities occurring in all experiments.